Change log for implantable medical device

ABSTRACT

A method and system for recording changes to programmable parameters in an implantable pulse generator. An executable program is stored in an implantable pulse generator. A parameter log is maintained in the implantable pulse generator, where the parameter log is used to record changes to the state of one or more programmable parameters of the executable program. When a change is detected in the state, from a first state to a second state, of the one or more programmable parameters the first state of the one or more programmable parameters changed to the second state are recorded in the parameter log. The parameter log is retrievable to allow for analysis of when and how changes took place to the executable program.

CROSS REFERENCE TO RELATED APPLICATION(S)

[0001] This application is a division of U.S. patent application Ser.No. 09/378,104, filed on Aug. 20, 1999, the specification of which isincorporated herein by reference.

FIELD OF THE INVENTION

[0002] This invention relates generally to the field of medical devices,and more particularly to implantable medical devices.

BACKGROUND

[0003] Cardiac rhythm management devices such as pacemakers,cardioverter/defibrillators, and combination devices typically includenumerous program parameters that affect device function, includingarrhythmia detection and therapy delivery. Device function can beadjusted to meet the needs of a patient by changing the programparameters. Some examples of program parameters include tachy mode (fordetecting and providing therapy for tachycardia) and brady mode (fordetecting and providing therapy for bradycardia). Changing programparameters such as tachy mode and/or brady mode activates or deactivatesmajor cardiac analysis and therapy functions of the device.

[0004] Most program parameters are adjusted using an external programmerrecorder/monitor that communicates with the implanted device viawireless telemetry through the skin. Program parameters may be turned onor off through the use of the external programmer. Other mechanisms mayalso modify parameter programming. For example, the device may, upondetection of an exhausted battery condition, disable some devicefunctions rather than delivery compromised therapy that may be erraticor potentially dangerous. Some devices respond to the presence of amagnet by inhibiting therapy momentarily, or permanently via magnetmaneuvers. Robust device designs perform periodic system integrityvalidation including program parameters. The device may alterprogramming to correct integrity errors. These types of changes to theprogram parameters may have a profound effect on the overall operationof the implanted device.

[0005] When a patient visits their physician for routine periodic devicefollow-ups, the device is interrogated using the external programmerrecorder/monitor. During this interrogation, a review is made ofparameter programming to assure that the device settings are appropriatefor the patient cardiac condition. When parameters are not as expected(e.g., a program parameter has been turned off, or there is analteration in programmable values the program parameter is using,), theclinician must investigate to discover how and why this occurred andtake corrective action. Knowing why and when the parameter programmingchanged is important information to assess the situation. When thisinformation is limited or incomplete, it places doubt on the assessmentand the reliability of the device. Therefore, a need exists forunderstanding how and why parameter programs have been affected duringthe operation of a cardiac rhythm management device.

SUMMARY OF THE INVENTION

[0006] As explained in detail below, the present subject matter isdirected to a method and system for providing a log maintained within animplantable medical device that records changes to the operation of theimplantable medical device. The log includes entries made by theimplantable medical device when operating parameters for executableprograms within the medical device and/or the operating state of theimplantable medical device change. Logging these types of changes areimportant in diagnosing how and why changes occurred in the operation ofthe implantable medical device.

[0007] In one embodiment of the present subject matter, an executableprogram is stored in an implantable pulse generator. The executableprogram includes one or more programmable parameters that have a firststate. The implantable pulse generator further includes a parameter log.The parameter log is used to record changes to the state of theprogrammable parameters for the executable program. Changes to the statecan include turning the executable program on or off, or makingalterations to programmable values used by the executable program. Whenthese types of changes are detected, the first state of the one or moreprogrammable parameters changes to a second state. The first state ofthe one or more programmable parameters changed to the second state isthen stored in the parameter log. Then, when it is discovered thatchanges have occurred to the programmable parameters, the log of thesechanges can be reviewed by the physician to more easily discover how andwhy the changes occurred.

[0008] Changes recorded in the log include changes to the execution(e.g., turned on or turned off) of the programs for the programmableparameters. Additionally, recorded changes can include those relatingthe use of a programmable parameter to deliver a “STAT” shock to apatient. Also, events in which the implantable pulse generator initiatesan electronic circuitry reset program to test its circuitry and programsettings is also recorded in the log. Additional events logged includewhen the implantable pulse generator is partially or totally disabledwith use of a magnet or when the implantable pulse generator terminatedan executable program due to a battery malfunction or expiration. Inaddition to storing why changes occurred to the programmable parameters,the time and the date of the change to the parameters is also recordedin the log.

BRIEF DESCRIPTION OF THE DRAWING

[0009]FIG. 1 is a flow chart illustrating one embodiment of the presentsubject matter;

[0010]FIG. 2 is a flow chart illustrating one embodiment of the presentsubject matter;

[0011]FIG. 3 is a schematic view of an implantable pulse generator and amedical device programmer according to one embodiment of the presentsubject matter; and

[0012]FIG. 4 is a block diagram of an implantable pulse generatoraccording to one embodiment of the present subject matter.

DETAILED DESCRIPTION

[0013] In the following detailed description, references are made to theaccompanying drawings that illustrate specific embodiments in which theinvention may be practiced. Electrical, mechanical, programmatic andstructural changes may be made to the embodiments without departing fromthe spirit and scope of the present invention. The following detaileddescription is, therefore, not to be taken in a limiting sense and thescope of the present invention is defined by the appended claims andtheir equivalents.

[0014] The embodiments of the present subject matter illustrated hereinare described as being included in an implantable pulse generator. Inone embodiment, the implantable pulse generator is an implantablecardioverter defibrillator, which may include numerous pacing modesknown in the art. Alternatively, it is also possible to implement thepresent subject matter in an implantable cardiac pacemaker. Furthermore,although the present invention is described in conjunction with animplantable pulse generator having a microprocessor-based architecture,it will be understood that the implantable pulse generator (or otherimplanted device) may be implemented in any logic based, customintegrated circuit architecture, if desired.

[0015] The present subject matter provides for a log to be maintainedwithin an implantable medical device. The log includes entries made bythe implantable medical device when operating parameters for executableprograms within the medical device and/or the operating state of theimplantable medical device change. Logging these types of changes areimportant in diagnosing how and why changes occurred in the operation ofthe implantable medical device. For example, an implantable medicaldevice may be programmed to operate in a first state (i.e., a firstmode). At a later time, the first state of the implantable medicaldevice is changed due to an external influence, factor and/or signal.This later influencing signal has the effect of changing the operationof the implantable from the first state to a second state. The secondstate of the implantable device can include changes to the operatingparameters of programs being executed within the implantable pulsegenerator, the termination of programs being executed within theimplantable pulse generator, and/or the complete shut-down of theimplantable device.

[0016] Executable programs are provided within the circuitry of theimplantable medical device to direct the operation of the device.Executable programs suitable for controlling and operating implantablepulse generators are known. These programs can include those designed toanalyze and provide therapy for bradycardia (e.g., Brady Mode), atrialfibrillation, atrial tachycardia, supraventricular tachycardia, andventricular fibrillation, congestive heart failure therapy, and otherprograms intended to treat cardiac arrhythmia and conditions.

[0017] A “Tachy Mode” program is an additional example of an executableprogram implemented in an implantable pulse generator and designed toanalyze and provide therapy to treat tachyrhythmia episodes. When theTachy Mode program is in operation, it analyzes cardiac complexes sensedin one or more sensed cardiac signals to determine the existence of atachycardia episode and, if programmed to do so, to direct the deliveryof therapy to terminate the tachycardia episode. In one embodiment, thestate of the Tachy Mode program, or other executable programs, can bealtered through the use of a medical device programmer. Altering thestate of the Tachy Mode program can be accomplished by delivering one ormore signals to the implantable pulse generator. Altering the state ofan executable program, such as the Tachy Mode program, can includebeginning the execution of the program, terminating (e.g., stopping) theexecution of the program, and/or changing programmable parametersassociated with the program.

[0018] Changes to the state of one or more programs within animplantable pulse generator are logged, or recorded, by the implantablepulse generator when they occur. In one embodiment, the changes loggedinclude the parameter values and/or settings prior to the change instate of the executable program. For example, if at a first time of zero(0) a first parameter of an executable program has a first value. At asecond time after the first time (t+0) a change occurs in the value ofthe first parameter the implantable medical device system logs, orrecords, the first value of the first parameter. Subsequent changes arealso identified and logged by the system. The changes to the state ofthe executable program can then be reviewed by retrieving the log.Information provided in the log can then be useful in determining howthe change occurred, what change occurred, when the change occurred andwhy the change occurred.

[0019] Executable commands, or signals, from a medical device programmerinstructing the implantable pulse generator to deliver one or moreshocks of electrical energy, such as pacing level pulses, cardioversionand/or defibrillation shocks also initiate changes which are recorded inthe log. For example, when a change is initiated in an executableprogram for the purpose of delivering a “STAT” shock (pacing,cardioversion, and/or defibrillation pulse) the change to the executableprogram (i.e., executing the program which initially turned off) islogged. Additionally, changes made to an executable program and/or theoperation of the implantable pulse generator through the use of amagnetic signal, such as using a, magnet, to disable the operation ofthe implantable medical device are also logged in the implantable pulsegenerator.

[0020] Referring now to FIG. 1, there is shown one embodiment of amethod according to the present subject matter. At 100 an executableprogram is stored in an implantable pulse generator. In one embodiment,the executable program is stored in a memory circuit within theimplantable pulse generator and is executed within the electroniccircuitry of the implantable pulse generator under the control of amicroprocessor. The implantable pulse generator further includes aparameter log. In one embodiment, the parameter log is a list containingthe state of an executable program prior to a change in the state of theexecutable program, when (e.g., time and date) the change to the stateoccurred along with additional information that will be described ingreater detail below.

[0021] The executable program stored and executed within the implantablepulse generator includes one or more programmable parameters having afirst state. In one embodiment, the first state of the one or moreprogrammable parameters includes being used with the executable programor the state of being not being used when the executable program isterminated (e.g., not executed). At 120, the implantable medical devicethen analyzes the first state of the one or more programmable parametersto detect a change to a second state of the one or more programmableparameters. In one embodiment, a change in the first state to the secondstate of the one or more programmable parameters includes a change inthe operational status of the executable program as previouslydiscussed.

[0022] Once a change is detected, the first state of the one or moreprogrammable parameters changed to the second state is stored in theparameter log at 140. So in one embodiment, the state of the one or moreprogrammable parameters that were actually changed to the second stateare logged in the parameter log. The parameter log also is used torecord when there is a change to all the one or more programmableparameters, such as when the executable program is (e.g., the Tachy Modeprogram) either intentionally or accidentally activated or terminated.

[0023] In one embodiment, the state of the one or more programmableparameters is changed from a first state to a second state bydeactivating the executable program in the implantable pulse generator.Examples of deactivating the executable program include terminating theexecutable program when the implantable pulse generator receives amagnetic signal. In one embodiment, the magnetic signal is received by aswitch coupled to the electronic circuitry of the implantable pulsegenerator. The change in the state of the programmable parameters isthen recorded in the parameter log. In the present example, thetermination of the executable program and/or the deactivation of theimplantable pulse generator is recorded in the parameter log.

[0024] In an additional embodiment, the state of the one or moreprogrammable parameters is changed from a first state to a second stateby the exhaustion of the power supply to the implantable pulsegenerator. For example, implantable pulse generators typically include abattery. When the energy supply from the battery expires, theimplantable pulse generator ceases to operate. As a result, executableprogram(s) within the pulse generator terminate. As this process isoccurring, the electronic circuitry within the pulse generator detectsthe change to the first state to the second state as the executableprogram ceases to operate. The change in the state of the programmableparameters is then recorded in the parameter log. In the presentexample, the termination of the executable program and/or thedeactivation of the implantable pulse generator is recorded in theparameter log.

[0025] Alternatively, the state of the one or more programmableparameters is changed from a first state to a second state by theexecution of an electronic circuitry reset program stored in theimplantable pulse generator. The change in the state of the programmableparameters is then recorded in the parameter log. In the presentexample, the execution of the electronic circuitry reset program isrecorded in the parameter log. A log of the execution of the electroniccircuitry reset program is then stored in the parameter log.

[0026] Referring now to FIG. 2, there is shown an additional embodimentof a method according to the present subject matter. At 200 a medicaldevice programmer is used to establish a communication link between theimplantable pulse generator and the medical device programmer. A firstsignal is then transmitted from the medical device programmer andreceived by the implantable pulse generator which changes the firststate of the one or more programmable parameters to the second state at220. Once the change is detected, the first state of the one or moreprogrammable parameters changed to the second state is stored in theparameter log at 240.

[0027] In one embodiment, the first signal transmitted to and receivedby the implantable pulse generator controls executable programscontained with the implantable pulse generator. For example, the firstsignal from the medical device programmer can instruct the electroniccircuitry of the implantable pulse generator to terminate running anexecutable program. Alternatively, the first signal from the medicaldevice programmer can instruct the electronic circuitry of theimplantable pulse generator to change one or more programmableparameters used in the execution of an executable program. When thesetypes of changes occur, the values and/or states of the parameters priorto the change are recorded in the parameter log.

[0028] In addition to recording changes to the parameter values and/orstates, information related to one or more electrical energy shocksdelivered under the control of the medical device programmer is recordedin the parameter log. In one embodiment, the medical device programmeris used to generate and transmit a second signal which is received bythe implantable pulse generator. The second signal instructs theelectronic circuitry of the implantable pulse generator to generate theone or more electrical shocks. In one embodiment, the one or moreelectrical shocks include pacing level shocks, cardioversion levelshocks and/or defibrillation level shocks.

[0029] The medical device programmer is also able to transmit a firstsignal to cause the electronic circuitry of the implantable pulsegenerator to execute an electronic circuitry reset program. When theelectronic circuitry reset program is executed, the first state of theone or more programmable parameters is considered changed and theoccurrence of this event is logged in the parameter log. In oneembodiment, the electronic circuitry reset program is a hierarchicalseries of programs which first test the integrity of parameter valuesand/or states in executable programs. Based on the results of this firsttest, if the parameter values and/or states are within acceptable rangesthe programs designated to be operating are executed. Alternatively, ifone or more of the parameter values and/or states are not withinacceptable ranges, one or more programs contained within electroniccircuitry of the implantable pulse generator attempt to correct theerror(s). If this is successful, the programs are executed. If this isnot successful, the values and/or states of the parameters are replacedwith nominal, or default, settings and the program(s) are executed.

[0030] In addition to logging changes in an executable program,executable commands, or signals, from a medical device programmerinstructing the implantable pulse generator to deliver one or moreshocks of electrical energy, such as pacing level pulses, cardioversionand/or defibrillation shocks are also logged. Furthermore, changes madeto an executable program and/or the operation of the implantable pulsegenerator through the use of a magnetic signal, such as using a magnet,to disable the operation of the implantable medical device are alsologged in the implantable pulse generator. Additionally, execution ofintegrity correction programs within the implantable pulse generator isalso recorded in the parameter log.

[0031] Also, along with logging changes of state in the parameter valuesand/or states, additional information is also provided and stored in theparameter log. For example, the additional information provided andstored in the parameter long includes supplying a date and a time whenthe change in the first state is detected. Additionally, the parameterlog maintains a record of a predetermined number of previous changesmade to the parameter values and/or state. For example, thepredetermined number is a value of at least two (2), where four (4) isan acceptable number. Thus, the first state of the parameters isrecorded when a change is detected to a second state. Similarly, thesecond state of the parameters is recorded when a change is detected toa third state. This type of recording of the state of parameterscontinues to occur until the parameter log has recorded thepredetermined number of changes to the parameters. Additionally, besidesstoring only the parameters that have changed from one state to a nextstate, the one or more programmable parameters unchanged from one stateto the next state (e.g., from the first state to the second state) arealso stored in the parameter log.

[0032] In one embodiment, the parameter log stored in the implantablepulse generator is accessible though the use of a medical deviceprogrammer. The medical device programmer allows for one or more commandsignals to be sent to the implantable medical device. Upon receiving thecommand signals the implantable pulse generator down loads, ortransfers, information contained in the parameter log to the medicaldevice programmer. The medical device programmer is then used to viewthe contents of the parameter log gathered by the implantable pulsegenerator.

[0033] Referring now to FIGS. 3 of the drawings, there is shown oneembodiment of an implantable pulse generator 300. In the presentembodiment, the implantable pulse generator 300 is an implantablecardiac defibrillator 302 electrically and physically coupled to atleast one intracardiac catheter 304. In one embodiment, the intracardiaccatheter 304 includes one or more pacing electrodes and one or moredefibrillation electrodes positioned on the intracardiac catheter 304.

[0034] The intracardiac catheter 304 is used to sense one or morecardiac signals which contain cardiac complexes each indicative of atleast a portion of a cardiac cycle. Electronic circuitry containedwithin the implantable cardiac defibrillator 302 is used to analyze thesensed cardiac complexes to determine the occurrence of an arrhythmicepisode. Based on the analysis of the cardiac complexes in the cardiacsignals, the electronic circuitry within the implantable cardiacdefibrillator 302 delivers one or more electrical pulses to electrodeson the one or more intracardiac catheters under certain predeterminedconditions to treat the arrhythmic episode.

[0035] In one embodiment, the intracardiac catheter 304 is anendocardial lead that is releasably attached to the cardiacdefibrillator 302. The intracardiac catheter 304 has an elongate bodywith a proximal end 308 and a distal end 310 and is shown as having apacing electrode 312 located at, or adjacent, the distal end 310 of theintracardiac catheter 304. In one embodiment, the pacing electrode 312is a tip electrode positioned at the distal end 310 of the intracardiaccatheter 304. Alternatively, the pacing electrode 312 is an annular, ora semi-annular ring electrode positioned adjacent the distal end 310.

[0036] The intracardiac catheter 304 also includes one or moredefibrillation electrodes. In one embodiment, the intracardiac catheter304 has a first defibrillation electrode 314 and a second defibrillationelectrode 316, where the first defibrillation electrode 314 and thesecond defibrillation electrode 316 are defibrillation coil electrodesas are known in the art. The first defibrillation electrode 314 isspaced apart and proximal from the pacing electrode 312, and the seconddefibrillation electrode 316 is spaced apart and proximal from the firstdefibrillation electrode 314.

[0037] Referring now to FIG. 4, there is shown an embodiment of a blockdiagram of the implantable cardiac defibrillator 302. The implantablecardiac defibrillator 302 includes electronic control circuitry 402 forreceiving one or more cardiac signals and delivering electrical energyto the one or more electrodes. The electronic control circuitry 402includes terminals, labeled with reference numbers 404, 406, and 408 forconnection to electrodes attached to the surface of the intracardiaccatheter 304. The pacing electrode 312 is electrically connected toterminal 404 and to the electronic control circuitry 402 through anelectrically insulated conductor provided within the elongate body ofthe intracardiac catheter 304. The first defibrillation electrode 314and the second defibrillation electrode 316 are connected to terminals406 and 408, respectively, and to the electronic control circuitry 402through electrically insulated conductors provided within the elongatebody of the intracardiac catheter 304.

[0038] In one embodiment, the electronic control circuitry 402 of thecardiac defibrillator 302 is encased and hermetically sealed in ahousing 410 suitable for implanting in a human body. In one embodiment,titanium is used for the housing 410, however, other biocompatiblehousing materials as are known in the art may be used. A connector block412 is additionally attached to the housing 410 of the cardiacdefibrillator 302 to allow for the physical and the electricalattachment of the intracardiac catheter 304 and the electrodes to thecardiac defibrillator 302 and the encased electronic control circuitry402.

[0039] The electronic control circuitry 402 of the cardiac defibrillator302 is a programmable microprocessor-based system, with a microprocessor412 and a memory circuit 414, which contains parameters for variouspacing and sensing modes and stores data indicative of cardiac signalsreceived by the electronic control circuitry 402. In one embodiment, thememory circuit 414 stores the parameter log and one or more executableprograms used by the implantable cardiac defibrillator 302 to analyzeand treat detected arrhythmic episodes. In addition to storing the oneor more executable programs, one or more programmable parameters havinga first state are also stored for the executable programs.

[0040] A communication circuit 416 is additionally coupled to theelectronic control circuitry 402, the memory circuit 414 and themicroprocessor 412 to allow the cardiac defibrillator 302 to establish acommunication link between the cardiac defibrillator 302 and a medicaldevice programmer 420. In one embodiment, the communication circuit 416and the medical device programmer 420 use a wire loop antenna 422 and aradio frequency telemetric link, as is known in the art, to receive andtransmit signals and data to and from the medical device programmer 420and the electronic control circuitry 402. In this manner, a firstsignal, including programming commands and/or instructions, istransmitted from the medical device programmer 420 and received by thecommunication circuit 416 to change the first state of the one or moreprogrammable parameters to the second state. Additionally, storedcardiac data, including the parameter log, pertaining to sensedarrhythmic episodes are transferred to the medical device programmer 420from the cardiac defibrillator 302.

[0041] The embodiment of the cardiac defibrillator block diagram showsthe pacing electrode 304 and the first defibrillation electrode 314coupled to a sense amplifier 426 to allow for bipolar sensing andpacing. The output of the sense amplifier 426 is shown connected to anR-wave detector 430. These components serve to sense and amplifyR-waves, and apply signals indicative thereof to the microprocessor 412.Among other things, microprocessor 412 responds to the R-wave detector430 by providing pacing signals to an electrical pulse generator circuit432 coupled to the microprocessor 412, as needed according to theprogrammed pacing mode. In one embodiment, the electrical pulsegenerator circuit 432 provides pacing level pulses to terminals 404 and406, which connect to the pacing electrode 304 and the firstdefibrillation electrode 314 for bipolar cardiac pacing. Power to thecardiac defibrillator 302 is supplied by an electrochemical battery 454that is housed within the cardiac defibrillator 302.

[0042] The first defibrillation electrode 304 and the seconddefibrillation electrode 306 are coupled to a sense amplifier 440, whoseoutput is connected to a cardiac morphology detector 444. Thesecomponents serve to sense and amplify QRS-complexes, and apply signalsindicative thereof to the microprocessor 412. In one embodiment, thecardiac morphology detector 444 includes an analog filter for filteringcardiac signal noise sensed by the electrodes. The cardiac signals arethen bandlimited before arriving at an analog-to-digital filter. Thecardiac signals are then A/D converted into a digital signal andsubsequently received by the microprocessor 412. The microprocessor 412responds to the sensed cardiac signals by providing electrical energypulses (cardioversion and/or defibrillation pulses) from the electricalpulse generator circuit 432.

[0043] In one embodiment, the medical device programmer 420 is used toproduce a second signal that when received by the communication circuit416. Upon receiving the second signal, the microprocessor 412 controlsthe electrical pulse generator circuit 432 to generate one or moreelectrical energy shocks. In one embodiment, the one or more electricalenergy shocks produced are pacing level shocks. Alternatively, the oneor more electrical energy shocks are cardioversion and/or defibrillationlevel shocks. After a second signal from a medical device programmer hasbeen used to produce electrical energy shocks, the microprocessor 412stores information related to the one or more electrical energy shocks(e.g., type of shocks delivered, strength of the shocks delivered, etc.)in the device log. Additionally, the second signal instructing theimplantable pulse generator to deliver one or more shocks of electricalenergy also initiates changes to the programs which are recorded in thelog. For example, when a change is initiated in an executable programfor the purpose of delivering a “STAT” shock (pacing, cardioversion,and/or defibrillation pulse) the change to the executable program (i.e.,executing the program which initially turned off) is logged.

[0044] Executable commands, or signals, from a medical device programmerinstructing the implantable pulse generator to deliver one or moreshocks of electrical energy, such as pacing level pulses, cardioversionand/or defibrillation shocks also initiate changes which are recorded inthe log. For example, when a change is initiated in an executableprogram for the purpose of delivering a “STAT” shock (pacing,cardioversion, and/or defibrillation pulse) the change to the executableprogram (i.e., executing the program which initially turned off) islogged.

[0045] The cardiac defibrillator 302 further includes a parameteranalysis circuit 460 coupled to the memory circuit 414, where theparameter analysis circuit 460 analyzes the first state of the one ormore programmable parameters to detect a change in a first state to asecond state of the one or more programmable parameters. When changes tothe programmable parameter states are detected (e.g., the change of oneor more programmable parameters from the first state to a second state),the state and/or value of the parameters prior to the change are storedin the parameter log by the microprocessor 412 in the memory circuit 414which is coupled to both the microprocessor 412 and the parameteranalysis circuit 460.

[0046] In one embodiment, the first signal received by the communicationcircuit 416 controls the executable program. For example, the firstsignal received by the communication circuit 416 can direct themicroprocessor 412 to terminate one or more executable programs beingperformed in implantable cardiac defibrillator 302. Alternatively, thefirst signal received by the communication circuit 416 changes thestatus and/or value of programmable parameters used by executableprograms in the implantable cardiac defibrillator 302.

[0047] The electronic control circuitry of the implantable pulsegenerator further includes a clock from which both a time and a date areprovided to the parameter log. In one embodiment, the clock is includedin the microprocessor 412 to provide information relative to time,including the time and the date of when changes in state to theprogrammable parameters occur. When changes to the parameter stateoccur, the microprocessor 412 stores the time and the date in theparameter log when the state of the one or more programmable parametersis changed.

[0048] Referring again to FIG. 3, there is shown one embodiment of amedical device programmer 320. As previously mentioned, one embodimentof the medical device programmer 320 for the implantable cardiacdefibrillator 302 takes the form of an external controller as are knownin the art. The medical device programmer 320 is designed to communicatewith an implantable medical device, such as the cardiac defibrillator302, via radio frequency telemetry. The medical device programmer 320has programmer electronic circuitry, including a microprocessing unitand related circuitry, such as digital memory, which is coupled to agraphics display screen 324.

[0049] In one embodiment, the medical device programmer 320 comprises anouter housing 328 which is made of a thermal plastic or other suitablelightweight durable material. The graphics display screen 324 isdisposed on the upper surface of housing 330. The graphics displayscreen 324 folds down into a closed position when medical deviceprogrammer 320 is not in use, thereby reducing the size of medicaldevice programmer 320 and protecting the display surface of graphicsdisplay screen 324 during transportation and storage.

[0050] In an additional embodiment, the external programmer additionallyhas a floppy disk drive and/or a removable disk drive and a hard drivedisposed within the housing. Air vents are provided at various points inthe housing so that an internal fan can circulate air within the housing328 and prevent overheating of components therein.

[0051] The medical device programmer 320 is shown with the graphicsdisplay screen 324 positioned in one of a plurality of possible openpositions such that a display on the graphics display screen 324 isvisible to a user situated in front of the medical device programmer320. In one embodiment, the graphics display screen 324 is of the LCD orelectroluminescent type. The graphics display screen 324 is operativelycoupled to the electronic circuitry disposed with the housing 328 and isadapted to provide a visual display of graphics and/or data undercontrol of the programmer electronic circuitry.

[0052] The medical device programmer 320 further includes a user inputdevice coupled to the electronic circuitry. In one embodiment, the userinput device is the graphics display screen 328, which is provided withtouch-sensitive capability, such that a user can interact with theprogrammer electronic circuitry by touching the display area on thegraphics display screen 328 with a stylus 340, or even the user'sfinger. In one embodiment, the touch-sensitive graphics display screenis primary input for the medical device programmer 320. The medicaldevice programmer 320 further includes a programming head 344, which isplace over a patient's body near the implant site of an implanteddevice, such as the cardiac defibrillator 302, in order to establish atelemetry link between the cardiac defibrillator 302 and the medicaldevice programmer 320. The telemetry link between the cardiacdefibrillator 302 and the medical device programmer 320 allows theelectronic circuitry coupled to the graphics display screen to becoupled to the electronic control circuitry of the cardiac defibrillator302. The programming head 344 is coupled to the electronic circuitry ofmedical device programmer 320 and a receiver circuit for receivingsignals from the communication circuit indicative of cardiac signals bya cable 350.

[0053] The stylus 340 used to interact with the touch-sensitive graphicsdisplay screen 324 is coupled to the programmer electronic circuitrywithin the housing 328 by a cable 354. Alternatively, the medical deviceprogrammer 320 may be equipped with a conventional computer “mouse”-typepointing device or a trackball, rather than a stylus. In the absence ofeither a stylus or a mouse, on-screen cursor control for enabling userinteraction with medical device programmer 320 may be facilitatedthrough cursor control keys 360 (arrow keys or the like) disposed on themedical device programmer 320.

[0054] The medical device programmer 320 further includes a receivercircuit for receiving signals from the communication circuit indicativeof cardiac signals. Through the telemetric contact with the cardiacdefibrillator 302, the medical device programmer 320 is capable ofcapturing and storing recorded electrocardiogram data transmitted fromthe cardiac defibrillator 302 and displaying the electrocardiogram dataon its graphics display screen 324.

[0055] This application is intended to cover any adaptations orvariations of the present invention. It is manifestly intended that thisinvention be limited only by the claims and equivalents thereof.

We claim:
 1. A method, comprising: storing an executable program in animplantable pulse generator, where the implantable pulse generatorincludes a parameter log and the executable program includes one or moreprogrammable parameters having a first state; detecting a change in thefirst state of the one or more programmable parameters to a secondstate; and storing in the parameter log the first state of the one ormore programmable parameters changed to the second state.
 2. The methodof claim 1, including establishing a communication link between theimplantable pulse generator and a medical device programmer;transmitting a first signal from the medical device programmer to changethe first state of the one or more programmable parameters to the secondstate; and receiving the first signal to change the first state of theone or more programmable parameters to the second state.
 3. The methodof claim 2, where transmitting the first signal includes controlling theexecutable program.
 4. The method of claim 3, where controlling theexecutable program includes terminating the executable program; andstoring a log of the executable program termination.
 5. The method ofclaim 3, where controlling the executable program includes activatingthe executable program; and storing a log of the executable programactivation.
 6. The method of claim 2, including generating one or moreelectrical energy shocks upon receiving a second signal; storing in theparameter log information related to the one or more electrical energyshocks; and storing a log of the second signal.
 7. The method of claim2, where the implantable pulse generator includes an electroniccircuitry reset program and transmitting the first signal from themedical device programmer to change the first state of the one or moreprogrammable parameters includes executing the electronic circuitryreset program when the first signal is received.
 8. The method of claim1, including terminating the executable program when the implantablepulse generator receives a magnetic signal; detecting the changeincludes detecting when the executable program terminates due to themagnetic signal; and storing a log of the magnetic signal in theparameter log.
 9. The method of claim 1, where the implantable pulsegenerator includes a battery, and terminating the executable programwhen the battery expires; detecting the change includes detecting whenthe executable program terminates due to the expired battery; andstoring a log of the expired batter in the parameter log.
 10. The methodof claim 1, including providing additional information to the parameterlog; and storing the additional information in the parameter log. 11.The method of claim 10, where providing additional information includessupplying a date and a time when the change in the first state isdetected.
 12. The method of claim 1, including detecting the executionof an electronic circuitry reset program in the implantable pulsegenerator; and storing a log of the execution of the electroniccircuitry reset program in the parameter log.
 13. The method of claim 1,including detecting a change in the second state of the one or moreprogrammable parameters to a third state; and storing in the parameterlog the second state of the one or more programmable parameters changedto the third state.
 14. The method of claim 1, including storing in theparameter log the first state of the one or more programmable parametersunchanged to the second state.
 15. The method of claim 1, includingdetecting the execution of an integrity correction program in theimplantable pulse generator; and storing a log of the execution of theintegrity correction program in the parameter log.
 16. An implantablepulse generator, comprising: a memory circuit to store a parameter logand an executable program, where the executable program includes one ormore programmable parameters having a first state; a parameter analysiscircuit coupled to the memory circuit, where the parameter analysiscircuit analyzes the first state of the one or more programmableparameters to detect a change in the first state to a second state ofthe one or more programmable parameters; and a microprocessor coupled tothe memory circuit and the parameter analysis circuit, where themicroprocessor stores the first state of the one or more programmableparameters changed to the second state in the parameter log.
 17. Theimplantable pulse generator of claim 16, including a communicationcircuit coupled to the microprocessor, where the communication circuitestablishes a communication link between the implantable pulse generatorand a medical device programmer, and the medical device programmertransmits a first signal that is received by the communication circuitto change the first state of the one or more programmable parameters tothe second state.
 18. The implantable pulse generator of claim 17, wherethe first signal received by the communication circuit controls theexecutable program.
 19. The implantable pulse generator of claim 18,where the first signal terminates the executable program.
 20. Theimplantable pulse generator of claim 16, including an electrical pulsegenerator circuit coupled to the microprocessor, where the medicaldevice programmer produces a second signal received by the communicationcircuit that causes the microprocessor to control the electrical pulsegenerator circuit to generates one or more electrical energy shocks, andthe microprocessor stores information related to the one or moreelectrical energy shocks in the parameter log.
 21. The implantable pulsegenerator of claim 16, where the microprocessor incudes an internalclock to provide information relative to time, including a time and adate, and where the microprocessor stores the time and the date in theparameter log when the first state of the one or more programmableparameters is changed to the second state.
 22. A method, comprising:storing an executable program in an implantable pulse generator, whereinthe executable program includes at least one programmable parameterhaving a first state; storing a parameter log in the implantable pulsegenerator; detecting an accidental change in the first state of the atleast one programmable parameter to a second state; and storing in theparameter log the first state of the at least one programmableparameters accidentally changed to the second state.
 23. The method ofclaim 22, wherein detecting the accidental change includes detecting oneof an accidental deactivation of the executable program and anaccidental activation of the executable program.
 24. The method of claim22, wherein storing the parameter log includes: establishing acommunication link between the implantable pulse generator and a medicaldevice programmer; and transmitting the parameter log stored in theimplantable pulse generator to the medical device programmer.
 25. Themethod of claim 24, wherein establishing the communication linkincludes: transmitting a first signal from the medical device programmerto change the first state of the one or more programmable parameters tothe second state; and receiving the first signal to change the firststate of the one or more programmable parameters to the second state.26. The method of claim 22, wherein detecting the accidental changeincludes detecting a non-programmer initiated change from the firststate of the one or more programmable parameters to the second state.27. The method of claim 22, wherein detecting the accidental changeincludes detecting a expiration of energy supplied by a battery in theimplantable pulse generator.
 28. The method of claim 22, whereindetecting the accidental change includes detecting execution of anelectronic circuitry reset program.
 29. The method of claim 22, whereindetecting the accidental change includes detecting termination of theexecutable program.
 30. The method of claim 22, wherein detecting theaccidental change includes detecting use of a magnetic signal to controloperation of the implantable pulse generator.
 31. The method of claim22, wherein storing includes recording execution of an integritycorrection program in the implantable pulse generator.
 32. The method ofclaim 22, wherein detecting the accidental change includes detecting achange due to an influence external to the implantable pulse generator.33. A system including an implantable pulse generator, programmer and acommunication link between the implantable pulse generator and theprogrammer, the implantable pulse generator comprising: an executableprogram in an implantable pulse generator, wherein the executableprogram includes one or more programmable parameters having a firststate and a second state; a parameter log for storing a change in astate of the one or more programmable parameters; the programmercomprising means for producing a first signal to change the first stateof the one or more programmable parameters to the second state, thefirst signal being transmitted to the implantable pulse generator by thecommunication link; and the implantable pulse generator furthercomprising: means for receiving the first signal to change the firststate of the one or more programmable parameters to the second state;and means for detecting a change in the first state of the one or moreprogrammable parameters to the second state, the change being stored inthe parameter log.
 34. The system of claim 33, wherein the means fordetecting includes means for detecting a change includes means fordetecting an accidental change from the first state of the one or moreprogrammable parameters.
 35. The system of claim 33, wherein the meansfor detecting includes means for detecting a non-programmer initiatedchange from the first state of the one or more programmable parameters.36. A method, comprising: storing an executable program in a cardiacrhythm management device, wherein the cardiac rhythm management deviceincludes a parameter log and the executable program includes one or moreprogrammable parameters having a first state; transmitting a signal froma medical device programmer to change the first state of at least oneprogrammable parameter to a second state; detecting a change of the atleast one programmable parameter to the second state; and storing in theparameter log the first state of the at least one programmableparameters changed to the second state.
 37. The method of claim 36,wherein storing the executable program includes storing the executableprogram in an implantable device.
 38. The method of claim 36, whereindetecting the change of the at least one programmable parameter to thesecond state includes detecting a change due to an influence external tothe cardiac rhythm management device.
 39. A cardiac rhythm managementdevice, comprising: a sensor for sensing cardiac signals; an electricalpulse generation circuit; a control circuit operable connected to boththe sensor to receive sensed cardiac signals and the electrical pulsegeneration circuit; and a memory operably connected to the controlcircuit, wherein the memory stores data indicative of sensed cardiacsignals, an executable program used by the control circuit, parametersfor the executable program, a device activity log, and a parameterchange log.
 40. The device of claim 39, wherein the parameter change logstores a first state of a parameter when the parameter is changed to asecond state.
 41. The device of claim 40, wherein the sensed cardiacdata includes arrhythmic episodes, and wherein the device activity logstores information related to one or more electrical energy shocksdelivered by the pulse generation circuit.